The Elk, as one might expect, have many natural rivals: the Grizzlies, the goats/Battleborn, the Scarecrows, and of course the Malamutes - but those are all predators or objects that mostly scare off deer-like animals in general. But the Newfoundland Berserkers are also a natural and significant rival for the Elk -- not only as humans that hunt and kill Elk, but also for being yet another Canadian team in tandem with their natural mascot rivalry with the Elk. One might argue, "okay, then why aren't the Malamute the greatest rival for Regina? They're also from Canada." But most teams in the SMJHL can at least rally against the Berserkers as other fellow animals or others under threat from them. Contextually, the Kelowna Knights don't quite fill the same thematic niche - they're strictly military combatants and probably wouldn't wear all their fancy knight armor out to slay elk. Similarly, nobody uses giant boats to hunt elk, and raptors didn't exist at the same time as non-megafauna-type Elk, so of course they wouldn't be natural rivals.

If it isn't clear, I have no historical context for these rivalries. Sorry.